Non-slip non-accumulating continuous wire drawing machine

ABSTRACT

A wire drawing machine has a plurality of drawing dies each associated with a drawing block powered by a direct current electric motor, all the motors being connected in parallel and having current supply controlling circuitry which insures that the sum of all of the motor speeds are constant and that all torques are equal except for a proportionality factor.

United States Patent Hoorelbeke [451 July 9, 1974 1 NON-SLIPNON-ACCUMULATING CONTINUOUS WIRE DRAWING MACHINE Inventor: LucHoorelbeke, Kortrijk, Belgium Assignee: N. V. Bekaert S.A., Zwevegem,

Belgium Filed: July 14, 1972 Appl. No.2 271,724

[30] Foreign Application Priority Data July 16, 1971 Belgium 770100 US.Cl 72/288, 72/289, 72/19 int. Cl. B2lc 1/12 Field of Search 72/19, 29,279, 280, 288,

References Cited UNITED STATES PATENTS Vicaire 72/2 88 1,914,833 6/ 1933 Nacken 2,124,518 7/1938 Marquart.... 2,321,612 6/1943 Nye 2,708,0245/1955 Bryden 2,759,139 8/1956 Few 3,518,859 7/1970 Brinkeborn 3,586,2216/197 1 Rosen 226/1 Primary Examiner-Charles W. Lanham AssistantExaminerM. J. Keenan Attorney, Agent, or FirmShlesinger, Arkwright,Garvey & Dinsmore 1 ABSTRACT A wire drawing machine has a plurality ofdrawing dies each associated with a drawing block powered by a directcurrent electric motor, all the motors being connected in parallel andhaving current supply controlling circuitry which insures that the sumof all of the motor speeds are constant and that all torques are equalexcept for a proportionality factor 4 Claims, 1 Drawing Figure ws Win S5[Sn This invention relates to a non-slip non-accumulating continuouswire drawing machine with adjustable back-pull containing a number ofdrawing dies and drawing blocks, whereby each drawing block is driven bya direct current motor with external excitation and whereby theinterconnection of the motors and the design of the control mechanismare such that the sum of the speeds of all motors remains constant andthat, except for a proportionality factor, the torques connected to themotors remain equal to each other. Nonaccumulating means that the wireis not pulled over transfer pulleys between the successive blocks inorder to carry out speed regulations.

This invention also relates to other kinds of machines, such as hot andcold rolling mills, and so on b. the torques remain equal to each otherexcept for a proportionality factor: Q C, r C2 l c,.=k,.c.

.Since externally'excited current motors are used for driving thevarious blocks of the wire drawing machine, and takinginto account thebasic equation of the externally excited direct current motor, equations(1) and (2) may also be expressed as follows basic equation of directcurrent motor:

"I l 1 1a 2 2/ 2 2 "n ll Il (I) where U, U,, are the terminal voltagesof the motors m I D are the fluxes generated by the field windings ofthe motors m m,, k, k are constants. KICDIII C2 2 2 2 u n n n ("l nconstant In order to obtain the above-mentioned advantages, viz,automatic compensation, or to obtain a differential wire drawingmachine, equations l and (2) must always be met. Asimilar wire drawingmachine for which equations (1') and (2) are always met, is known, viz,a wire drawing machine with series-connected driving motors m, m, m,,,such as described in theBelgian Pat. No. 481.842.

However, this known machine has important disadvantages, viz,:

In case of wire breakageduring the drawing process, threading-up isaccomplished, after welding the wire, by an appropriate change of thetorques acting on the motors. This change is effected by altering thefield current in the field windings of these motors. So, the torquesconnected to each motor for a certainstationary regime must be changedand readjusted in order to reobtain the stationary regime. This is acomplicated and time-absorbing process.

In the case of series-connected drivingmotors, it is necessary to usespecial transformers for the classic motors (440 volts), and to developspecial low tension motors; this is the most used solution.

In addition, since the current in series-connected moto'rs is very high,the lives of the motors is prejudiciallyinfluenced'. Indeed, thenecessary power P U]. As U is generally low, a high current I is used.

The danger of racing of the motors in case of wire breakage is also adisadvantage. In case of breakage'all motors stop, whereas one of themotors starts racing. In stationary regime, the total applied voltage Uis distributed over the motors or a volt age U/n is applied to eachmotor.

Because all motors stop except one, the latter will try to reach such aspeed that its E.M.F. is equal to the totalvoltage U or, in other words,this motor will try to runn times faster.

In the case of series fed motors, it is necessary to stretch the wirebetween the successive blocks so that the machine may start again afterhaving been stopped when the wire hung loose or sagged between thesuccessive'blocks. This happens by a change of the torques acting on themotors. This change is effected by altering the field current in thefield windings. Also this is a complicated and time-absorbing process.

Working with less passes than normally provided for the machine alsoentails important difficulties. For example, a principal n-hole machinefrom which three passes are eliminated. In case of series feed, eachmotor to be eliminated must be bridged by means of a contactor whichmust be able to deviate the large series current.

It is an object of the invention to provide a wire drawing machine ofthe aforesaid type wherein also equations (1") and (2) are always metand, moreover, wherein the aforesaid disadvantages of the known machinesare eliminated.

' Therefore, it is proposed that for a wire drawing machine of theaforesaid type, these direct current motors m, m, are connected inparallel, whereby each motor m m,, is provided with a self-controlledrectifier G G for converting the feed from the al' temating currentsystem, so that each motor m m is provided with a direct voltage outputcircuit 0 a m, up to m,- in position III, all motors m,,t,

0,, for the separation of the terminal voltages U U,,, whereby theoutput terminals of these transformers O, 0,, are connected in seriesfor summing up or obtaining EU, and that the regulating mechanism of theassembly is provided with an adjustable direct current source U for thedetermination of a reference voltage U and, furthermore, with anamplifier P, whereby the input of the amplifier is determined by thedifference U EU, and the output of this amplifier is transferred to thecontrol circuit of the rectifiers G, (7,, or is used as reference valueI, for the determination of the currents I, I,,. i

The regulating mechanism of a wire drawing machine according to theinvention, of which the motors m, m,, are connected in parallel, isdesigned in such a way that when making a correction in order to meetequation l or EU, constant, equation (2') is automatically met, or, inother words, in order to meet EU, constant (-1 a correction is made bychanging the currents I, I 1,, in the motors m, I m,, in such a way thatequations (2) are always met. This is obtained by taking the outputvalue of amplifier P as a reference value for the determination ofcurrents], 1,, in the motors m, m,,, or, in other words, this signifiesthat the control circuits of the rectifiers G, G,, are connected inparallel'on the output of amplifier P.

In a wire drawing machine according to the invention, a switch S S,, isprovided between the output of amplifier P and the input of each controlcircuit of the rectifiers of the motors, and the control mechanism ofeach motor m, m,, isprovided with a handle H, H,, having four positions,I (up), II (down), Ill (left), and IV (right), whereby these switches S,S,, and this handles H, H,, are mutually connected by means of knownrelay connections in such a manner that for any motor m,, only motor m,is energized in position I, all motors m, m,, in position II, all motorsp to m,, in position IV, and that, when released, each handle H,automatically takes the zero position.

A wire drawing machine as set forth in the invention offers thefollowing advantages:

When wire breakage occurs, wire threading after welding can be done byconnecting only the motors that serve for carrying out this operation,since the control circuit of each motor can be easily interruptcd. Thishappens by moving the handles H, H,, or in other words by controllingthe switches S, S,,. The torques C, C,, acting on these motors are nolonger altered by a change of the cur rent in the field windings. Thisconsiderably simplifies the service of the machine.

Because of the parallel feed of the motors, the threephase alternatingcurrent system (380 volts) can be used without using transformers forthe classic direct current motors (440 volts).

The parallel feed of the motors also pennits maintaining the current ineach motor at a low level, which is of importance for a long motor life.

In case of wire breakage, there is no danger for racing of the motors. Aclassic motor (440 volts) will maximally run percent above its normalworking "speed, since the applied voltage can maximally be 510 volts ina three-phase alternating current system of 380 volts.

Since each motor m, m,, has a proper current control with its own timeconstant, the machine according to the invention may run in withsomewhat loose wires on various blocks. This saves time and difiicultieswhen starting.

Working with a smaller number of passes than normally provided for themachine does not entail any difficulties. It is only necessary tointerrupt the control circuit of the motors 'or blocks to be isolated.

The invention will now be described in greater detail, with reference tothe accompanying drawing, the single FIGURE of which is a circuitdiagram of the machine as set forth in the invention.

The machine illustrated in the drawing is a non-slip non-accumulatingcontinuous wire drawing machine with adjustable back-pull containing ndrawing dies T,

...T,-. .T andndrawingblocksW, ..W,-...W,,. Each block W, W,- W,, isdriven by a separate direct current motor m, m, m,, with externalexcitation. These motors m, m,, are connected in parallel. The nominalvoltage of these motors is for example 440 volts. Each motor m, m,, isprovided with a self-controlled rectifier G, G,, for converting the feedfrom the three-phase alternating current system, for example analternating voltage of 380 volts. The rectifiers G, G,, are controlledby means of a thyristor circuit. It is assumed that for a certainstationary regime, the motors m, in, m,, should produce torques C,.. .C,C,, at speeds n, n,- n,,. Except for a proportionality factor, thesetorques are determined by the product of the fluxes I 1 4 produced bythe field windings P, P, P,, and the armature currents I, I, 1,, or C,=k,l ,1, ..C,-

=k, I ,-I,- and C,, =k,, I ,,I,,. The fluxes I 1 CI in the fieldwindings P, P, P,, are determined by using the resistors R, R, R,, ofthese windings and the armature currents I, I, 1,, in the motors bycurrent amplification of the adjustment.

Each motor m, m,, is provided with a direct tension direct tensiontransformer O, 0,, for the galvanic separation of the terminal voltagesU, U,,-of the motors, whereby the output clamps of these rectifiers O,0,, are series-connected, so that except for a proportionality factor,the sum or 2U, tained.

The regulating mechanism of the machine is provided with an adjustabledirect tension source U for the determination of a reference tension Uwhich corresponds to a certain sum of the speeds n, n, ...+n,,or2U,

Furthermore, the control mechanism is provided with an error amplifierP, whereby the input value of the amplifier is determined by thedifference U EU, and the output value of this amplifier is transferredto the control circuit of the rectifiers G, G,,. This means that theoutput value of the amplifier P is used as reference value 1,, for the,determination of currents I, I, 1,, in the motors.

Switches S, S,- S,, are provided between the output of amplifier P andthe input of each control circuit of the motors. Moreover, each motor m,m, m,, is provided with a handle H, H,- H, having four positions, I(up),II(down), III(left), IV(right). The switches S, S,, and these handlesI-I, H, are connected by means of known relay connections in such a waythat for any motor m,- only motor m, is energized in position I, allmotors m, m,, in position II, all motors m, up to m,- in position III,and all motors m,,, up

to m in position IV. When released, each handle H,- automatically takesthe zero position, or, in other words, the associated switch S,- isautomatically opened.

f. power supply means for supplying electrical energy to each of theelectrical motors and to which they are connected in parallel,

g. the power supplymeans having a variable electrical output which isdependent upon a control voltage supplied thereto,

h. the total speed output signal of the summing means being applied tothe power supply means as a control voltage to control the electricalenergy output to the electrical motors. 2. The plural stage processingassembly as set forth in claim 1, wherein:

tween switches S S and the associated handles Hi H in order to obtainother controls from switches S S in other handle positions.

What we claim is:

l. A plural stage processing assembly for a length of metal, comprising;

a. a plurality of metal deforming stations through which a length ofmetal is successively passed,

b. takeup and drawing means at each deforming station and in engagementwith the length of metal,

c. a separate electrical driving motor connected to each of the takeupand drawing means,

(1. motor speed measuring meas connected to each motor for measuring thespeed thereof and producing an output signal dependent on motor speed,

e. summing means to which the outputs of all of the motor speedmeasuring means are interconnected for producing a total motor speedsignal representing the sum of all of the output motor signals,

a. the power supply means is an amplifier through which alternatingcurrent is supplied,

b. each of the electrical motors is a direct current motor,

c. each of the motors has a self-controlled rectifier means connectedbetween the source and the motor.

3. The plural stage processing assembly as set forth in claim 1,wherein:

a. each metal deforming station is a wire drawing die,

h. each of the takeup and drawing means is a drawing block. 4. Theplural stage processing assembly as set forth in claim 1, wherein:

a. automatic switch means is provided in each of the motor circuits foreither energizing or deenergizing the motor.

1. A plural stage processing assembly for a length of metal, comprising:a. a plurality of metal deforming stations through which a length ofmetal is successively passed, b. takeup and drawing means at eachdeforming station and in engagement with the length of metal, c. aseparate electrical driving motor connected to each of the takeup anddrawing means, d. motor speed measuring meas connected to each motor formeasuring the speed thereof and producing an output signal dependent onmotor speed, e. summing means to which the outputs of all of the motorspeed measuring means are interconnected for producing a total motorspeed signal representing the sum of all of the output motor signals, f.power supply means for supplying electrical energy to each of theelectrical motors and to which they are connected in parallel, g. thepower supply means having a variable electrical output which isdependent upon a control voltage supplied thereto, h. the total speedoutput signal of the summing means being applied to the power supplymeans as a control voltage to control the electrical energy output tothe electrical motors.
 2. The plural stage processing assembly as setforth in claim 1, wherein: a. the power supply means is an amplifierthrough which alternating current is supplied, b. each of the electricalmotors is a direct current motor, c. each of the motors has aself-controlled rectifier means connected between the source and themotor.
 3. The plural stage processing assembly as set forth in claim 1,wherein: a. each metal deforming station is a wire drawing die, b. eachof the takeup and drawing means is a drawing block.
 4. The plural stageprocessing assembly as set forth in claim 1, wherein: a. automaticswitch means is provided in each of the motor circuits for eitherenergizing or de-energizing the motor.